Which system would you check if you want to ensure effective operation of the weapons?

The Military Aircraft Systems (MASS) stands for Mission Equipment and Ammunition Systems Subsystem. This system is critical for ensuring the effective operation of the aircraft's weaponry. It includes all components involved in the management, targeting, and delivery of munitions, making it paramount to confirm that these systems are operational when assessing weapons functionality.

Proper operation of the MASS ensures that munitions can be accurately deployed as intended during missions. This covers both the electronic and mechanical aspects of weapon systems, which are essential for precision and safety. If the MASS system is checked and verified to be functioning correctly, it provides assurance that the weapons will operate effectively when needed.

The other systems mentioned may have important roles in overall aircraft operation or safety but do not directly pertain to the effective operation of the weapons themselves. For example, the fuel management system is primarily concerned with fuel supply rather than weapon delivery, the emergency stores jettison switch is more about safety and emergency procedures, and control surfaces are related to flight control rather than the weapon systems' effectiveness.